1. Field of the Invention
The present invention generally relates to a multilayer wiring board and its manufacturing method, and more particularly to a coreless interposer board and its manufacturing method in which a plurality of resin layers and a plurality of wiring layers are alternately arranged in laminated formation.
2. Description of the Related Art
In recent years, development of SIP (System In Package) of various types is carried out in order to meet the demands for high-speed, high-density LSI packages. SIP is a kind of the technology for incorporating two or more semiconductor chips to a single semiconductor package. Development of an interposer board on which two or more semiconductor chips are carried is also briskly performed with the development of SIP.
For example, the interposer board is a wiring board in which wiring layers made of metal, such as copper, and insulating layers made of resin, such as an epoxy or polyimide resin, are laminated alternately.
Usually, a plurality of interposer boards are formed in a comparatively large base board collectively, and thereafter a dicing process is performed to cut the base board into the respective interposer boards.
Japanese Laid-Open Patent Application No. 10-027971 discloses the cutting process of an organic thin-film multilayer wiring board in order for preventing the removal of the organic thin film from the substrate after cutting and the cleavage of the substrate after cutting.
Japanese Laid-Open Patent Application No. 10-135157 discloses the multilayer wiring board and its manufacturing method in order for preventing the removal of the interlayer insulation film in a dicing process.
In the conventional methods mentioned above, it is necessary to cut mechanically the resin layers for which the laminated formation is carried out with a dicing blade etc. By the external force applied in the dicing process, the resin layers for which the laminated formation is carried out may be damaged, or the film removal may occur in the interface of the respective resin layers.
FIG. 28 shows the composition of a conventional multilayer wiring board. The multilayer wiring board 20 of FIG. 28 is a multilayer wiring board on which a plurality of wiring boards (in this example, two pieces) are arranged sidewise, and the first through fourth resin layers 1-4 and the first through fourth wiring layers 5-8 in each wiring board are laminated alternately and these layers do not have a core substrate.
When the multilayer wiring board 20 is cut into the respective wiring boards, the cutting area 9 indicated by the dotted line in FIG. 28 is mechanically cut with a dicing blade.
In the case of the multilayer wiring board 20 of FIG. 28, all the resin layers 1-4 are mechanically cut by the dicing blade. In the mechanical cutting, all the resin layers tend to be damaged, and the removal of each resin layer in the interface easily occurs.
Even if the removal of the resin layer in the resin interface at the time of cutting is avoided, there is the problem that reliability of the respective wiring boards deteriorates due to the resin damage at the time of cutting.
In order to avoid the problem, for example, Japanese Laid-Open Patent Application No. 10-027971 proposes the method of cutting mechanically the multilayer wiring board with a dicing blade after the resin layers are removed by a laser beam cutting.
However, in the proposed method of Japanese Laid-Open Patent Application No. 10-027971, the protection of the cross-section of the resin layers at the time of cutting mechanically is not taken into consideration. Moreover, the introduction of the laser machine for cutting the resin layers, the increase in the manufacturing processes needed, etc. are necessary, which will raise the cost. Thus, the proposed method is not feasible in the actual production line.
On the other hand, the proposed method of Japanese Laid-Open Patent Application No. 10-135157 is effective for the multi-layer wiring board having the core substrate on which the resin layers and the wiring layers are held.
However, in the case of the coreless wiring board in which all the layers are formed of resin and which does not have a core substrate, it cannot be said that the proposed method of Japanese Laid-Open Patent Application No. 10-135157 provides adequate effects of preventing the removal of the interlayer insulation film when cutting mechanically the wiring board.